Apparatus for jacking up and supporting a structure

ABSTRACT

A jacking system includes a wheeled hydraulic power unit having an operating handle, and at least two extendable jack units which are identical. 
     Each jack unit is adapted to rest upon the ground, and the power unit can be wheeled into (or out of) engagement with the jack unit. When engaged with a jack unit, the power unit is capable of extending (or raising) the jack unit; a ratchet on the jack unit then locks it in its extended position. A manual control on the power unit is coupled to the jack unit (when the two units are interengaged) for releasing the ratchet, so that the power unit can then lower the jack stand to its retracted position.

BACKGROUND OF THE INVENTION

The previously known methods of jacking up and supporting a vehicle orstructure have left much to be desired.

For example, in order to work underneath an automobile it is oftennecessary to raise the vehicle and support it at two or more separatepoints. Previously known methods of accomplishing this result havegenerally been dangerous and unsafe, since there would be at least onepoint of time at which the person doing the work would have to place aportion of his body underneath the vehicle even though the vehicle wasnot firmly and safely supported.

The object and purpose of the present invention is to provide a methodand apparatus for jacking up and supporting a vehicle or structure,which will substantially eliminate the safety hazards inherent inpreviously known methods and apparatus.

PRIOR ART

Prior art references known to the applicant include the following:

    ______________________________________                                        No.        949,331      Scholle                                               No.      2,258,825      Thompson                                              No.      2,404,577      Jackson                                               No.      3,664,635      Kincaid                                                          829,333      HAMPSON                                                        1,280,472      HOPKINS                                                        1,280,473      HOPKINS                                                        1,863,105      GARNIER                                                        2,370,681      MUELLER                                                        2,529,292      GREENFIELD                                                     3,834,669      REID                                                           4,251,056      MANIGLIA                                              ______________________________________                                    

SUMMARY OF THE INVENTION

According to the present invention a two-part system of apparatus isused for jacking up and supporting a vehicle or structure. The apparatusincludes a single machine known as the power unit or jack, and a numberof identical devices each of which constitutes an extendible jack stand.

Each of the extendible jacks stands is ordinarily in an initialcondition in which its members are telescoped or retracted. It iscapable, however, of being vertically extended for the purpose ofraising a load. When thus extended, it is also capable of being lockedin that position.

According to the invention the power unit or jack is so designed andarranged as to be capable of positioning an extendible jack stand in adesired location, and also of controlling the operation of that jackstand after it has been positioned. More specifically, the power unit iscapable of handling and controlling the jack stand in such a way that itis not necessary for human hands to be placed directly upon the jackstand.

The method of the invention is carried out as follows. The power unit isutilized in order to place a plurality of the jack stands in selectedlocations underneath the vehicle or structure that is to be raised. Thepower unit is then utilized to control the jack stands one at a time, sothat each jack stand is vertically extended and then locked in itsextended position. In this manner the entire vehicle or structure israised without the necessity of placing human hands, or any portion ofthe bodies of operating personnel, underneath the vehicle or structure.When the vehicle or structure is to be lowered, the power unit is againutilized for controlling the jack stands one at a time, in such mannerthat each jack stand is first unlocked and then retracted to its initialcondition.

In accordance with the invention the presently preferred form of jackstand includes horizontal top and bottom plates, a pair of verticallydisposed telescoping members attached to corresponding ones of theplates, and ratchet means carried by the telescoping members forreleasably locking them in a selected position of longitudinalextension.

According to the presently preferred form of the invention the powerunit includes a frame having wheel support means, and which is adaptedto be selectively moved towards or away from the vicinity of a jackstand. The power unit is provided with expansible lifting means adaptedto be inserted between the plates of the jack stand. The power unit alsoincludes power means for expanding the expansible lifting means so as tothereby raise the top plate of the jack stand. The power unit alsoincludes a manually operated control for the power means, and a manuallyoperated control for releasing the ratchet means of the jack stand.

To ensure effective cooperative action of the power unit with the jackstand, it is also preferred to equip both units with alignment means sothat the power unit may be moved into engagement with the jack stand ina predetermined relative position. Since the ratchet is in the jackstand, while the ratchet release is a manual control carried by thepower unit, it is also necessary to provide an appropriate coupling fromthe ratchet release control to the ratchet mechanism itself. Thisratchet release coupling mechanism is preferably located directly inconjunction with the alignment mechanisms of both the power unit and thejack stand.

DRAWING SUMMARY

FIG. 1 is a top plan view of the presently preferred form of power unitor jack in accordance with the invention;

FIG. 2 is a side elevation view of the power unit of FIG. 1;

FIG. 3 is a side elevation view of the power unit and one of the jackstands when in their interengaged position, with the jack stand beingvertically extended;

FIG. 4 is a transverse cross sectional view of the jack stand taken onthe line 4--4 of FIG. 3, and also showing the interengaging parts of thepower unit;

FIG. 5 is a horizontal cross sectional view of the mechanism taken onthe line 5--5 of FIG. 4;

FIG. 6 is a fragmentary cross sectional view of the ratchet mechanism ofthe jack stand, showing its released position;

FIG. 7 is a view similar to the right-hand side of FIG. 5, showing theaction that occurs when the ratchet mechanism is being released;

FIG. 8 is a cross sectional view taken on line 8--8 of FIG. 4, andshowing the alignment mechanisms of both units of the apparatus;

FIG. 9 is a perspective view showing the apparatus of the presentinvention being used for raising the axle of a vehicle; and

FIG. 10 is a perspective view of a modified form of the jack and liftingmeans.

DETAILED DESCRIPTION--GENERAL OPERATION

FIGS. 1-9, inclusive, of the drawings illustrate the presently preferredform of apparatus in accordance with the present invention. In general,the apparatus includes a single power unit PU and a plurality of jackstand units JU. FIG. 1 shows a top plan view of the power unit PU andalso shows in dotted lines a set of four jack stand units JU1, JU2, JU3,and JU4 which are so positioned as be transported by the power unit.Elsewhere in the drawings (with the exception of FIG. 3) only a singlejack stand unit is shown; therefore, in the other drawing figures thejack stand unit is simply referred to by its general designation, JU.

The operation of the apparatus is such that the power unit PU could beconsidered the "master" while the jack unit JU could be considered the"slave". That is, the hands of the operator are directly applied only tothe power unit, and the power unit is capable of transporting,positioning, raising, locking, unlocking, lowering, and withdrawing thejack stand unit. More importantly, all of these operations areaccomplished without the necessity for the human operator to place anypart of his anatomy underneath the vehicle or structure which is goingto be raised and supported by the jack stand units.

The power unit therefore has several manual controls, all of which arepositioned at its rearward end and conveniently available to theoperator. At its forward end it has mechanism for aligning it in apredetermined position relative to the jack stand unit, and also forlatching it in that position. Also at its forward end it has expansiblelifting means for raising or lowering the jack stand.

The power unit is also designed and arranged in such manner that itbecomes a vehicle for transporting a jack stand unit to or from adesired location. Further, in its presently preferred form the powerunit has a capacity for transporting four of the units JUsimultaneously.

JACK STAND UNIT (FIGS. 3-9)

In general, the jack stand unit JU includes a flat horizontal base plate10, a vertical frame 20 whose lower end is rigidly attached to the baseplate, a vertical shaft 30 which is arranged in telescoping relationshipwith the frame 20, and a horizontal top plate 40 which is rigidlyattached to the upper end of the shaft 30. Top plate 40 provides aload-bearing seat. All of the parts are made of a metal such as steel,and the telescoping members are preferably attached to the correspondingplates by means of welding. Both the vertical frame 20 and the verticalshaft 30 are made of hollow configuration, for greater structuraladvantage. Base plate 10 is simply a flat metal plate of square orrectangular configuration adapted to rest upon the ground G or othersupporting surface, providing a supporting base for the jack stand unit.

Frame 20 is of hollow rectangular configuration as best seen in FIGS. 5and 8. It has identical front or back walls 21 and identical side walls22. A rounded protuberance 23 is welded onto the outer surface of eachside wall 22 near its lower end, but spaced a certain distance above thebase plate 10. Protuberances 23 are used for aligning and latching thepower unit PU to the jack stand unit JU, as will later be described. Asmall distance above the protuberance 23 each of the side walls 22 alsohas a hole or opening 24 to receive a ratchet release pin, as will belater described.

The shaft 30 includes a pair of identical front or back plates 31. Italso includes a pair of identical ratchet plates 32 which provide a webstructure that interconnects the plates 31, in an arrangement similar toan I beam, except that the plates 32 are spaced apart a distance whichis about equal to the distance by which they are set inward from theends of the plates 31. The outer surfaces of the ratchet plates 32 carryratchet teeth 33. The shaft assembly 30 is of such a size as to fitinside the hollow frame 20, as clearly shown in FIGS. 5 and 8. The outersurfaces of the front or back plates 31 of shaft 30 then bear againstthe inner surfaces of front or back walls 21 of frame 20. The lateraledges of plates 31 are fitted fairly closely to the inner surfaces ofside walls 22 of the frame 20. The fit of shaft 30 inside the hollowframe 20 is sufficiently loose as to keep friction within reasonablelimits, but at the same time tight enough to ensure a moderatelyaccurate vertical alignment of the shaft 30.

Top plate 40 includes a load-bearing member 41 which is secured to theupper ends of plates 31, 32, and whose lateral expanse is sufficient tooverhang the side walls 22 of frame 20. The outer ends of load-bearingmember 41 are fitted with downwardly depending vertical flanges 42. Theload-bearing member 41 is in the general form of a flat plate, but itsupper surface has a slight concave curvature, as most clearly seen inFIG. 3, in order to most advantageously support a load such as a vehicleshaft V.

A pair of ratchet arms 50 are positioned inside the side walls 22 offrame 20 and extend from the pin openings 24 upward to somewhat near thetop of frame 20. Each of the ratchet arms 50 has a curved plate or tooth51 welded to its upper end. Near the upper end of each arm 50 a pivotpin 52 pivotally supports it from a bracket 53 that is in turn welded tothe interior surface of side wall 22. A ratchet spring 54, located abovethe bracket 53, is positioned between side wall 22 and ratchet tooth 51for purpose of urging the tooth 51 into engagement with one of theratchet teeth 33 carried by ratchet plate 32 of the shaft assembly 30. Aratchet release pin 55 extends horizontally through each of the openings24, see FIGS. 4 and 5, with its inner end being welded to the lower endof ratchet rod 50. The upper edges of the two ratchet plates 51 are atthe same elevation, and ratchet teeth 32 are arranged in pairs so thatthe ratchet mechanism provides vertical support for both of the plates32 in each vertical position that corresponds to a pair of the ratchetteeth 32. The ratchet mechanism provides a self-latching means forlocking the vertically telescoping frame members in a selected extensionposition.

The design of unit JU lends itself to the insertion of a pair of liftingjaws underneath the laterally projecting ends of the load-bearing member41, so that the jaws will be laterally retained by the flanges 42. Asthe load-bearing member 41 is moved upward, the shaft assembly 30 moveswith it, and downward movement is constrained by the ratchet mechanism.The ratchet mechanism can be released by pressing both of the ratchetrelease pins 55 inwardly at the same time. This action serves to releaseboth of the ratchet plates 51 from engagement with the ratchet teeth,thereby permitting the upper portion of the unit JU, i.e., shaftassembly 30 and top plate 40, to drop downwardly.

POWER UNIT (FIGS. 1-9)

Power unit or jack PU has a generally box-like frame 100 which is bestseen in FIG. 9 in conjunction with FIGS. 1 and 3. The frame 100 issupported on a pair of wheels 110 which are attached to its respectivesides. A pair of frame extensions 120 extend forward from the respectivesides of the frame 100, providing a generally U-shaped configuration inthe horizontal plane, as best seen in FIG. 1. The forward end portionsof the frame extension 120 provide latching arms that are particularlyadapted to be aligned with, and latched to, the jack stand unit JU.

Thus as seen in FIGS. 4 and 5 each of the frame extensions has anL-shaped configuration in the vertical plane, including a horizontalbottom plate 121 and a vertical outer or side plate 122. The verticalthickness of bottom plate 121 is such that it will slide upon the topsurface of base plate 10 of unit JU and yet fit beneath the protuberance23. In this connection it will be noted that, as best seen in FIG. 3,the frame extensions 120 are curved in a somewhat banana-shapedconfiguration, so that while the rear or main frame 100 is supported asubstantial distance above ground G by means of wheels 110, the bottomplates 121 at the forward ends of the frame extensions 120 aresubstantially horizontal at the elevation of the vertical gap betweenbottom plate 10 and protrusion 23 of unit JU.

The forward extremity of each bottom plate 121 is convexly curved at123, as best seen in FIG. 5. These curved forward ends of the bottomplates provide an automatic centering action when the power unit PU ispropelled into engagement with one of the units JU. At the point wherecurved extremity 123 ends, each of the bottom plates 121 has avertically disposed spring 125 welded to its upper surface. Spring 125is curved in the horizontal plane, as best seen in FIG. 5, and is soarranged as to capture the corresponding protuberance 23 in retainingrelationship therewith.

For purpose of propelling and controlling the power unit PU, it isequipped with a handle 130 which extends rearwardly and upwardly fromthe main frame 100. See FIGS. 3 and 9. Handle 130 has three differentmodes of operation. In one mode a switch 131, see FIG. 9, is moved intoits locked position so that handle 130 is locked in fixed relationshipto frame 100. This condition permits the power unit PU to be easilytransported from one place to another, since the operator simply pushesthe handle 130 downward by a sufficient amount so that the latch arms121, 122 will easily clear the ground and other obstructions. The handleis also kept in the locked position when the power unit is being broughtinto engagement with a jack stand unit JU. After the springs 125 havebecome latched around protuberances 23 of the unit JU, the lock 130 ismoved to its unlocked position.

When the handle is unlocked, it can be moved vertically in a pivotingmovement, and it can also be rotated. In either of these movements it ispowered by the hand H of the operator, see FIG. 9. Vertical arrows 132indicate the vertical pivoting movement of the handle 130, whilecircular arrow 133 indicates the rotating movement. The verticalmovement is used for pumping up, or supplying energy to, a hydrauliccylinder 140 carried within the main frame 100 of the power unit.Rotating movement of handle 130 is effective for actuating a releasevalve, not specifically shown, so that the pressure generated bycylinder 140 will be relieved. The mode of operation of both thehydraulic cylinder 140 and the actuating handle 130 are generallyconventional and well understood, and hence need not be furtherdescribed.

Power unit PU also includes a lifting frame 150, of generally box-likeconfiguration, which is supported within the main frame 100 by means ofpivot shaft 151. See FIGS. 3 and 9. The lifting frame 150 has two sideextensions 152, each providing a lifting arm, and thus giving thelifting frame a generally U-shaped configuration when seen in thehorizontal plane, as in FIG. 1.

The lifting frame 150 is pivoted in a vertical plane so as to raise thelifting arms 152, this action being accomplished by the forward movementof piston rod 141 driven forward by expansion within the cylinder 140,the piston rod 141 being secured to the lifting frame 150 at quite somedistance below the pivot shaft 151. The lifting arms 152 carrycorresponding lifting arms extensions 153, best seen in FIG. 3. Eachlifting arm extension 153 is slidably mounted in the correspondinglifting arm 152 for longitudinal extension thereof. A tie rod 154 hasits ends connected by pivot pins to the rearward end of the lifting armextension 153, and also to a properly selected point on the side wall122 of the corresponding latch arm, so that as the lifting arm is raisedits arm extension will move progressively forward. The purpose of thisarrangement is so that a jaw 155 carried on the forward end of liftingarm extension 153 will at all times remain vertically aligned above thebase of the jack stand.

Thus the lifting arm extension serves to correct the length of theassociated lifting arm as a function of the angularity through which thearm is pivoted. It is also necessary to progressively correct theangular position of the jaw 155. Thus the jaw 155 is supported by meansof a pivot pin 156 from the end of arm extension 153, and an alignmentrod 157 has its forward end welded to the jaw 155 while its rearward endrides in a curved slot 158 formed in the associated lifting arm 152. Theforward relative movement of arm extension 153, in conjunction with thecurvature of slot 158 as best seen in FIG. 2, causes jaw 155 toprogressively change its angular relationship to the arm extension asthe arm extension is being extended. The action is therefore such as tomaintain a constant angular position of jaw 155 relative to ground asthe load-bearing member 41 is elevated. This is illustrated in FIG. 3.It will be noted that the upper surface of jaw 155 is concavely curvedso as to engage the convexly curved under surface of load-bearing member41, thereby ensuring both effective alignment and effective support.

RAISING THE JACK STAND

In order to raise the jack stand the power unit PU must be brought intoalignment with the jack stand unit JU. With handle 130 in its lockedposition, the operator directs the power unit so that the bottom plates121 of latch arms 120 will slide upon the upper surfaces of plate 10 onopposing sides of the frame 20. Curved surfaces 123 cause the power unitto be automatically centered in a lateral direction, and springs 125engage the protuberances 23 with a moderately strong latching action soas to establish the correct longitudinal or forward position of thepower unit. When this is accomplished, the jaws 155 are automaticallylocated underneath the projecting ends of load-bearing member 41 andwithin the confines of the flanges 42 thereon. It will be noted in FIG.4 that the jaws 155 have inwardly offset portions 155a which fit withinthe flanges 42.

The operator now unlocks handle 130 by actuating the latch 131, andcommences a vertical pumping action. Energy accumulated within thecylinder 140 then drives the piston rod 141 in a forward direction so asto pivotally raise the lifting arms 152, together with their forwardextensions and associated jaws and adjustment mechanisms. Theload-bearing member 41, together with the load that it carries, islifted to whatever height is desired. When the raising of the jack iscompleted the handle 131 is rotated in a slow and cautious manner so asto partially relieve the lifting force of the jaws 155, thereby ensuringthat the nearest pair of the ratchet teeth 33 will reliably seat uponthe ratchet plates 51. The cylinder pressure is then further relieved,and the power unit may if desired be withdrawn from its engagement withthe jack stand unit so as to be used at another location.

LOWERING THE JACK STAND

In order to lower the jack stand the power unit must be brought into itsengagement position, and the lifting arms raised so that the jaws 155carry the full load of the load-bearing member 41. At that time a remotecontrol 160 carried on handle 130 of the power unit is actuated forpurpose of releasing the ratchet mechanisms in the jack stand. Remotecontrol device 160 consists simply of a cord or cable with a handle onits rearward end. Inside the frame 100 of the power unit the cord 160 isdivided into a pair of cords 161 which run along the upper surfaces ofbottom plates 121 of the corresponding latch arms of the power unit.Each cord 161 is capable of operating a cam mechanism that will, inturn, push the associated ratchet release pin 55 inwardly of the sidewall 22 of frame 20 of the jack stand unit.

The cam mechanism will now be described. A bracket 170 is attached toouter side wall 122 of the latch arm, extending inward from the upperedge of that side wall. A fixed vertical bolt or pin 171 extendsdownward from the bracket 170. A rotatable cam 172 is carried on thebolt or pin 171, cam 172 being in the same horizontal plane as theassociated ratchet release pin 55, as best seen in FIG. 4. A coil spring173 interacting between the bolt or pin 171 and the cam 172 serves tonormally retain the cam in a non-actuated position. The limit positionof the cam is established by screw 176 in side wall 122. Thecorresponding cord 161 is tied to an arm 174 which projects downwardfrom the underside of cam member 172. The non-actuated position of thecam members 172 is shown in FIGS. 4 and 5. FIG. 7 shows the actuatedposition in which the cords 161 have been pulled, thereby causing thecam member 172 to push the release pin 55 inwardly of frame 20. Thus thehole 24 and release pin 55 provide a means for disabling theself-latching action of the ratchet mechanism.

FIG. 6 shows the releasing action of the ratchet mechanisms. Since bothpins 55 are pushed inward at the same time, both ratchet plates 51 willrelease at the same time, or nearly so. Precise synchronization of therelease of the two sides of the ratchet mechanism is not required sincethe load on the load-bearing member 41 remains fully supported by thelifting arms until the ratchet release operation is fully completed.

It is necessary for the operator to continue pulling on cord 160 whilethe upper portion of the jack stand is being lowered. Otherwise the loadwould be locked in place by the very next pair of ratchet teeth 33.

TRANSPORTING MULTIPLE JACK STANDS

As indicated in FIG. 1, the power unit PU is capable of transportingfour of the jack stands JU. They are carried on the blades 121 of thelatching arms of the power unit, with the two protuberances 23 of eachjack stand unit resting on the upper surface of those blades. FIG. 3shows a jack stand JU which has been positioned and is in the course ofbeing vertically extended. It has a flat base plate 10. The base plate10' of the next jack stand of the series is shown in fragmentary form.Mating snap fastener elements 180, 181 are secured to the upper surfacesof the plates 10', 10, at their forward and rearward edges,respectively. When two or more jack stands are being transported by thepower unit, these snap fasteners keep them connected together in aseries.

When the first jack stand JU is installed and raised with a load on it,withdrawal of the power unit will not result in moving the jack stand.Rather, the springs 125 will slide away from the protuberances 23 of thefirst jack stand, and will later engage the protuberances 23 of thesecond jack stand. Continued withdrawal of the power unit will cause thesnap fastener 180, 181 to separate, since a relatively small force isrequired for that purpose. Thus, for the next installation of a jackstand, the second jack stand JU2 of the original series is alreadyproperly positioned in the power unit.

ALTERNATE FORMS

While in the presently preferred embodiment the power unit PU carries asingle hydraulic cylinder 140 to provide the power operation, otherarrangements are of course possible. For example, a pair of verticallyaligned cylinders carried by the power unit may be inserted between thetop plate 40 and bottom plate 10 of the jack stand unit JU and expandedvertically for the purpose of lifting the load.

An alternate type of arrangement is shown in FIG. 10. There aload-bearing seat 200 has its respective ends fastened to the upper endsof a horizontally spaced pair of vertical shafts 201. The verticalshafts 201 are mounted in telescoping relationship to the frame of thejack stand, not specifically shown. The power unit rather than beingequipped with a pair of lifting arms is then equipped with only a singlelifting arm 210, which is inserted between the pair of vertical shafts201 for engaging and raising the load-bearing seat 200.

The invention has been described in considerable detail in order tocomply with the patent laws by providing a full public disclosure of atleast one of its forms. However, such detailed description is notintended in any way to limit the broad features or principles of theinvention, or the scope of patent monopoly to be granted.

What is claimed is:
 1. A two-part jack system comprising, incombination: an extendible jack stand having a horizontal bottom plate,a horizontal top plate, a pair of vertically disposed telescopingmembers attached to corresponding ones of said plates, and ratchet meanscarried by said telescoping members for releasably locking said membersin a selected position of longitudinal extension;a power unit havingwheel support means and adapted to be selectively moved towards or awayfrom the vicinity of said jack stand, said power unit having expansiblelifting means adapted to be inserted between said plates of said jackstand; power means carried by said power unit for expanding orcontracting said expansible lifting means to thereby raise or lower saidtop plate; manually operated means carried by said power unit forcontrolling said power means; and manually operated means carried bysaid power unit for releasing said ratchet means when said top plate isto be lowered.
 2. A two-part jack system as claimed in claim 1 whichfurther includes alignment means on said power unit, and separatealignment means on said jack stand, said two alignment means cooperatingfor aligning said two units in a predetermined relative position;andmeans for releasably securing said two units together in saidpredetermined relative position.
 3. A two-part jack system as claimed inclaim 1 wherein said expansible lifting means includes a pair of latcharms adapted to be positioned upon said bottom plate on opposing sidesof said telescoping members, and a pair of lifting arms adapted toengage the undersurface of said top plate on opposing sides of saidtelescoping members.
 4. A two-part jack system as claimed in claim 3wherein said power means includes a single hydraulic cylinder, and meansfor lifting said pair of lifting arms in unison in response to a drivingforce provided by said cylinder.
 5. A two-part jack system as claimed inclaim 2 wherein said releasable securing means cooperates directly withsaid alignment means in securing said two units together.
 6. A two-partjack system as claimed in claim 5 which further includes coupling meanscooperatively associated with both said alignment means and saidreleasable securing means, and coupling said ratchet means of said jackstand with said manually operated means carried by said power unit forreleasing said ratchet means.
 7. A two-part jack system as claimed inclaim 2 wherein said releasable securing means cooperates directly withsaid alignment means in securing said two units together.
 8. A two-partjack system as claimed in claim 7 which further includes coupling meanscooperatively associated with both said alignment means and saidreleasable securing means, and coupling said ratchet means of said jackstand with said manually operated means carried by said power unit forreleasing said ratchet means.
 9. A two-part jack system as claimed inclaim 2 where said expansible lifting means includes a pair of latcharms adapted to be positioned upon said bottom plate on opposing sidesof said telescoping members, and a pair of lifting arms adapted toengage the undersurface of said top plate on opposing sides of saidtelescoping members.
 10. A system of apparatus for jacking up andsupporting a vehicle or structure, comprising, in combination:aplurality of extendible jack stand units, each having a supporting baseadapted to rest upon the ground, a load-bearing seat for engaging andlifting a load, telescoping vertical support members for supporting saidseat in a raised position above said supporting base, and means forlocking said telescoping members in any selected one of a series of suchraised positions; a power unit adapted to raise or lower a selected oneof said jack stand units, said power unit having means for removablylatching same to the selected jack stand unit, expansible means adaptedto be inserted between said supporting base and said load-bearing seatof the jack stand unit, and power means for causing said expansiblemeans to expand and thereby raise the load-bearing seat of theassociated jack stand unit; means controlled by said power unit andoperable when said load-bearing seat is in a raised position forunlocking said telescoping members while concurrently allowing saidexpansible means to contract; and all of said jack stand units beingidentical, whereby said power unit may be used with different ones ofthem in sequence.
 11. The system of apparatus claimed in claim 10wherein said power unit has wheel support means and is adapted to beselectively moved toward or away from the vicinity of a selected one ofsaid jack stand units.
 12. The system of apparatus claimed in claim 10wherein said power unit includes manually operable means for controllingsaid power means, and manually operable means for unlocking saidtelescoping members of the associated jack stand unit.
 13. The system ofapparatus claimed in claim 10 wherein said power unit includes alignmentmeans, and which further includes separate alignment means on each ofsaid jack stand units, the alignment means of said power unit and theselected jack stand unit cooperating for aligning said two units in apredetermined relative position; said latching means being operable toreleasably secure said two unit together in said predetermined relativeposition.
 14. Apparatus for jacking up and supporting a vehicle orstructure, comprising, in combination:an extendible jack stand having asupporting base adapted to rest upon the ground, a load-bearing seat forengaging and lifting a load, telescoping vertical support membersattached to said supporting base and said seat, respectively, forsupporting said seat, and means for locking said telescoping members inan extended position; a mobile hydraulic power unit having supportingwheels, expansible means adapted to be removably inserted between saidload-bearing seat and said supporting base, means for releasablylatching said power unit to said jack stand when said expansible meansis thus inserted, and power means for causing said expansible means toexpand so as to raise said load-bearing seat; and manually operablecontrol means on said power unit controlling the operation of said powermeans for raising said load-bearing seat, for selectively releasing saidmeans for locking said telescoping members in an extended position, andfor lowering said load-bearing seat after said locking means has beenreleased.
 15. Apparatus as claimed in claim 14 wherein said power unithas a handle and said manually operable control means are carried bysaid handle.
 16. Apparatus as claimed in claim 14 wherein said powerunit is adapted to transport said jack stand, to position said jackstand underneath a vehicle or structure, to selectively raise saidload-bearing seat of said jack stand, to selectively release saidlocking means of said jack stand, to selectively lower said load-bearingseat of said jack stand, and to retrieve said jack stand when its workhas been completed.
 17. Apparatus as claimed in claim 16 wherein saidpower unit has a handle and said manually operable control means arecarried by said handle.
 18. A jacking system comprising an extendiblejack stand adapted to rest upon the ground, a power unit selectivelyattachable to said jack stand for raising or lowering said jack stand,ratchet means on said jack stand for automatically maintaining saidstand in a raised position, wheeled support means fixedly attached tosaid power unit, and manual control means carried by said power unit andcoupled to said jack stand whenever said power unit is attached theretofor selectively releasing said ratchet means so as to permit said jackstand to be lowered.
 19. A jacking system as claimed in claim 18 whereinsaid extendible jack stand includes first and second verticallytelescoping members, one of said members carrying a pair of parallelplates which are spaced apart and each of which has a vertical series ofteeth formed thereon;the other of said telescoping members carrying apair of pivotally supported tooth members adapted to engage the teeth ofrespective ones of said plates; said manually controlled means of saidpower unit being operable for releasing both of said tooth members atthe same time.
 20. Apparatus for jacking up and supporting a vehicle orstructure, comprising, in combination:an extendible jack stand having asupporting base adapted to rest upon the ground, a load-bearing seat forengaging and lifting a load, telescoping vertical support membersattached to said supporting base and said seat, respectively, forsupporting said seat, and ratchet means for locking said telescopingmembers in an extended position; a mobile hydraulic power unit havingsupporting wheels, expansible means adapted to be removably insertedbetween said load-bearing seat and said supporting base, means forreleasably latching said power unit to said jack stand when saidexpansible means is thus inserted, and power means for causing saidexpansible means to expand so as to raise said load-bearing seat; andmanually operable means on said power unit coupled to said jack standfor selectively releasing said ratchet means when said telescopingmembers are in an extended position, said manually operable means alsocontrolling said power means for supporting said load-bearing seat in adownward movement after said ratchet means has been released. .Iadd.21.A two-part jack apparatus comprising, in combination: a jack standhaving a horizontal bottom plate, a horizontal top plate, a pair ofvertically disposed telescoping members attached to corresponding onesof said plates, and ratchet means carried by said telescoping membersfor releasably locking said members in a selected position oflongitudinal extension; a power unit adapted to be selectively alignedwith and releasably attached to said jack stand; said power unit havingexpansible lifting means adapted to be inserted between said plates ofsaid jack stand on opposite sides of said telescoping members; and powermeans carried by said power unit for expanding or contracting saidexpansible lifting means to thereby raise or lower said top plate;characterized by the feature that said power unit includes alignmentmeans, said jack stand having separate alignment means; said twoalignment means cooperating for aligning said two units in apredetermined relative position; and manually operated means carried bysaid power unit and remote from said power unit alignment means, forcontrolling said power means and for releasing said ratchet means whensaid top plate is to be lowered. .Iaddend. .Iadd.22. A two-part jackapparatus as claimed in claim 21 wherein said ratchet means includesspring means for automatically locking said telescoping members in anextended position. .Iaddend. .Iadd.23. A two-part jack apparatus asclaimed in claim 21 or 22 which further includes spring latch meanscooperating directly with said alignment means for releasably securingsaid two units together. .Iaddend. .Iadd.24. A two-part jack apparatusas claimed in claim 23 wherein said power unit includes a spaced pair oflatch arms adapted to slide over said bottom plate of said jack stand onrespective sides of said telescoping members, the forward inner ends ofsaid latch arms having said power unit alignment means comprising curvedsurfaces adapted to align said two units as they are being broughttogether, said alignment means of said jack stand including a pair ofprotuberances on respective sides of said telescoping members, and saidspring latch means comprising a pair of springs extending in parallelrelationship to respective ones of said latch arms for releasablyengaging respective ones of said protuberances. .Iaddend. .Iadd.25. Atwo-part jack apparatus as claimed in claim 23 wherein said expansiblelifting means includes a pair of latch arms adapted to be positionedupon said bottom plate, and a pair of lifting arms adapted to engage theundersurface of said top plate. .Iaddend. .Iadd.26. A two-part jackapparatus as claimed in claim 25 wherein said latch arms and saidlifting arms are part of a scissors mechanism. .Iaddend. .Iadd.27. Atwo-part jack apparatus as claimed in claim 25 wherein said power meansincludes a single hydraulic cylinder for actuating said scissorsmechanism. .Iaddend. .Iadd.28. A two-part jack apparatus as claimed inclaim 25 wherein one of said telescoping members of said jack stand is ahollow frame attached to said bottom plate and extending upwardlytherefrom, and the other of said telescoping members is a vertical shaftattached to said top plate and extending downwardly within said hollowframe;said jack stand also including a vertical series of ratchet teethcarried by said shaft, and a ratchet arm extending vertically upwardinside said frame, said ratchet arm having a curved tooth on its upperend and being pivotally mounted near said tooth on the interior wall ofsaid frame so that said tooth may move towards or away from said ratchetteeth. .Iaddend. .Iadd.29. A two-part jack apparatus as claimed in claim28 wherein said hollow frame of said jack stand has an opening formedtherein adjacent the lower end of said ratchet arm and at a fixedelevation above said bottom plate, whereby the horizontal movement of aratchet release member through said opening may effect the unlocking ofsaid ratchet arm. .Iaddend. .Iadd.30. A two-part jack apparatus asclaimed in claim 29 wherein said ratchet release member is secured tothe lower end of said ratchet arm. .Iaddend. .Iadd.31. A two-part jackapparatus as claimed in claim 30 wherein said jack stand includes twosuch series of ratchet teeth, two such ratchet arms, and said hollowframe has two such openings therein, one for each ratchet arm. .Iaddend..Iadd.32. A two-part jack apparatus as claimed in claim 31 wherein saidmanually operated means for controlling said power means, when a liftingaction is completed, locks said jack stand in place without any loaddemands on said power means. .Iaddend. .Iadd.33. A two-part jackapparatus as claimed in claim 31 wherein said power unit includesseparate manually operable means for releasing said ratchet means..Iaddend. .Iadd.34. A two-part jack apparatus as claimed in claim 33wherein, said separate manually operable means includes cam means forproviding a horizontal actuating force against a ratchet arm containedin said ratchet means, for selectively unlocking said telescopingmembers. .Iaddend. .Iadd.35. A two-part jack apparatus as claimed inclaim 34 which includes at least two identical ones of said jack stands..Iaddend. .Iadd.36. A two-part jack apparatus as claimed in claim 35wherein said power unit is capable of transporting, positioning,raising, locking, unlocking, lowering, and withdrawing a jack stand..Iaddend. .Iadd.37. A two-part jack apparatus as claimed in claim 36wherein said power unit is supported on wheels. .Iaddend. .Iadd.38. Atwo-part jack system comprising, in combination: an extendible jackstand having a horizontal bottom plate, a horizontal top plate, a pairof vertically disposed telescoping members attached to correspondingones of said plates, and ratchet means carried by said telescopingmembers for releasably locking said members in a selected position oflongitudinal extension;a power unit having support means, adapted to beselectively moved towards or away from the vicinity of said jack stand,said power unit having expansible lifting means adapted to be insertedbetween said plates of said jack stand; power means carried by saidpower unit for expanding or contracting said expansible lifting means tothereby raise or lower said top plate; manually operated means carriedby said power unit for controlling said power means; and manuallyoperated means carried by said power unit for releasing said ratchetmeans when said top plate is to be lowered. .Iaddend. .Iadd.39. Atwo-part jack system as claimed in claim 38 which further includesalignment means on said power unit, and separate alignment means on saidjack stand, said two alignment means cooperating for aligning said twounits in a predetermined relative position; andmeans for releasablysecuring said two units together in said predetermined relativeposition. .Iaddend. .Iadd.40. A two-part jack system as claimed in claim38 wherein said expansible lifting means includes a pair of latch armsadapted to be positioned upon said bottom plate on opposing sides ofsaid telescoping members, and a pair of lifting arms adapted to engagethe undersurface of said top plate on opposing sides of said telescopingmembers. .Iaddend. .Iadd.41. A two-part jack system as claimed in claim40 wherein said power means includes a single hydraulic cylinder, andmeans for lifting said pair of lifting arms in unison in response to adriving force provided by said cylinder. .Iaddend. .Iadd.42. A two-partjack system as claimed in claim 39 wherein said releasable securingmeans cooperates directly with said alignment means in securing said twounits together. .Iaddend. .Iadd.43. A two-part jack system as claimed inclaim 42 which further includes coupling means cooperatively associatedwith both said alignment means and said releasable securing means, andcoupling said ratchet means of said jack stand with said manuallyoperated means carried by said power unit for releasing said ratchetmeans. .Iaddend. .Iadd.44. A two-part jack system as claimed in claim 39wherein said releasable securing means cooperates directly with saidalignment means in securing said two units together. .Iaddend. .Iadd.45.A two-part jack system as claimed in claim 44 which further includescoupling means cooperatively associated with both said alignment meansand said releasable securing means, and coupling said ratchet means ofsaid jack stand with said manually operated means carried by said powerunit for releasing said ratchet means. .Iaddend. .Iadd.46. A two-partjack system as claimed in claim 39 where said expansible lifting meansincludes a pair of latch arms adapted to be positioned upon said bottomplate on opposing sides of said telescoping members, and a pair oflifting arms adapted to engage the undersurface of said top plate onopposing sides of said telescoping members. .Iaddend. .Iadd.47. A systemof apparatus for jacking up and supporting a vehicle or structure,comprising, in combination:a plurality of extendible jack stand units,each having a supporting base adapted to rest upon the ground, aload-bearing seat for engaging and lifting a load, telescoping verticalsupport members for supporting said seat in a raised position above saidsupporting base, and means for locking said telescoping members in anyselected one of a series of such raised positions; a power unit adaptedto raise or lower a selected one of said jack stand units, said powerunit having means for aligning and removably latching same to theselected jack stand unit, expansible means adapted to be insertedbetween said supporting base and said load-bearing seat of the jackstand unit, and power means for causing said expansible means to expandand thereby raise the load-bearing seat of the associated jack standunit; means controlled by said power unit and operable when saidload-bearing seat is in a raised position for unlocking said telescopingmembers while concurrently allowing said expansible means to contract;and all of said jack stand units being identical, whereby said powerunit may be used with different ones of them in sequence. .Iaddend..Iadd.48. The system of apparatus claimed in claim 47 wherein said powerunit has support means and is adapted to be selectively moved toward oraway from the vicinity of a selected one of said jack stand units..Iaddend. .Iadd.49. The system of apparatus claimed in claim 47 whereinsaid power unit includes manually operable means for controlling saidpower means, and manually operable means, remote from said power unitalignment means, for unlocking said telescoping members of theassociated jack stand unit. .Iaddend. .Iadd.50. The system of apparatusclaimed in claim 47 which further includes separate alignment means oneach of said jack stand units, the alignment means of said power unitand the selected jack stand unit cooperating for aligning said two unitsin a predetermined relative position; said latching means being operableto releasably secure said two units together in said predeterminedrelative position. .Iaddend. .Iadd.51. Apparatus for jacking up andsupporting a vehicle or structure, comprising, in combination:anextendable jack stand having a supporting base adapted to rest upon theground, a load-bearing seat for engaging and lifting a load, telescopingvertical support members attached to said supporting base and said seat,respectively, for supporting said seat, and means for locking saidtelescoping members in an extended position; a mobile hydraulic powerunit having supporting means, expansible means adapted to be removablyinserted between said load-bearing seat and said supporting base, meansfor releasably latching said power unit to said jack stand when saidexpansible means is thus inserted, and power means for causing saidexpansible means to expand so as to raise said load-bearing seat; andmanually operable control means on said power unit controlling theoperation of said power means for raising said load-bearing seat, forselectively releasing said means for locking said telescoping members inan extended position, and for lowering said load-bearing seat after saidlocking means has been released. .Iaddend. .Iadd.52. Apparatus asclaimed in claim 51 wherein said power unit has a handle and saidmanually operable control means are carried by said handle. .Iaddend..Iadd.53. Apparatus as claimed in claim 51 wherein said power unit isadapted to transport said jack stand, to position said jack standunderneath a vehicle or structure, to selectively raise saidload-bearing seat of said jack stand, to selectively release saidlocking means of said jack stand, to selectively lower said load-bearingseat of said jack stand, and to retrieve said jack stand when its workhas been completed. .Iaddend. .Iadd.4. Apparatus as claimed in claim 53wherein said power unit has a handle and said manually operable controlmeans are carried by said handle. .Iaddend. .Iadd.55. A jacking systemcomprising an extendible jack stand adapted to rest upon the ground, apower unit selectively attachable to said jack stand for raising orlowering said jack stand, ratchet means on said jack stand forautomatically maintaining said stand in a raised position, support meansfixedly attached to said power unit, and manual control means carried bysaid power unit and coupled to said jack stand whenever said power unitis attached thereto for selectively releasing said ratchet means so asto permit said jack stand to be lowered. .Iaddend. .Iadd.56. A jackingsystem as claimed in claim 55 wherein said extendible jack standincludes first and second vertically telescoping members, one of saidmembers carrying a pair of parallel plates which are spaced apart andeach of which has a vertical series of teeth formed thereon;the other ofsaid telescoping members carrying a pair of pivotally supported toothmembers adapted to engage the teeth of respective ones of said plates;said manually controlled means of said power unit being operable forreleasing both of said tooth members at the same time. .Iaddend. .Iadd.Apparatus for jacking up and supporting a vehicle or structure,comprising, in combination:an extendible jack stand having a supportingbase adapted to rest upon the ground, a load-bearing seat for engagingand lifting a load, telescoping vertical support members attached tosaid supporting base and said seat, respectively, for supporting saidseat, and ratchet means for locking said telescoping members in anextended position; a mobile hydraulic power unit having supportingmeans, expansible means adapted to be removably inserted between saidload-bearing seat and said supporting base, means for releasablylatching said power unit to said jack stand when said expansible meansis thus inserted, and power means for causing said expansible means toexpand so as to raise said load-bearing seat; and manually operablemeans on said power unit coupled to said jack stand for selectivelyreleasing said ratchet means when said telescoping members are in anextended position, said manually operable means also controlling saidpower means for supporting said load-bearing seat in a downward movementafter said ratchet means has been released. .Iaddend.